There can be several reasons why you would love to watch your favorite YouTube videos on a dark background with no extra page elements visible: it creates a cool “cinema watching” experience, it removes all clutter and moves the focus to the video.

With “lights” off you don’t feel yourself distracted by “related videos” to the right or users’ comments (which are usually a mess by the way). Full-screen mode could be a good solution to see the video only, but sometimes the video resolution doesn’t allow that. Besides, as you’ll see from the screenshots below, videos on the black background just look somehow nicer.

I was able to find 4 different browser extensions that allow you to dim the light for any YouTube video. Here they are :

1. YouTube Cinema

YouTube Cinema hides everything on the page except for the video and lets you easily select the background color (as well as the video size) from the handy bar on the right:

With this extension, the videos will open in YouTube Cinema mode by default. You will need to hold the CTRL key down while clicking to open a video in the usual mode.

Supported Browsers:

3. Turn Off The Lights

Turn Off the Lights is another cross-browser extension that adds some fun to YouTube video viewing.

Similar to the one above, it works via a little lamp icon (but this one is located in your bookmarks toolbar) that fades the page to dark and brings focus to the video. Clicking the icon again brings the light back on.

If you see no Lamp button after the installation, go to View > Toolbars > Customize in the menu and drag the “Turn Off the Lights” addon onto your toolbar.